In my code I used my root node which holds an animated 3d robot. This is working fine.

My problem now is that I want to use the QWidget inside a MainWindow and I just don´t get this to work.
The code I am using right now is;

widgetOSG->setParent(ui->widget);
ui->widget->show();

The whole code I posted is in my sourceFile from the MainWindow.cpp . I just used the standard MainWindow that
Qt Creator is creating when a new Qt Project is set up. widgetOSG is just a QWidget I created in the forms editor.

It looks like the scene is loaded into that QWidget. But I can´t see it.
One thing the compiler says is: